1. Field of the Invention
The present invention relates to disk head assemblies for supporting read/write heads adjacent rotating disks in disk drives and more particularly, to a swage mount for attaching a head suspension assembly to a head actuator arm.
2. Description of Related Art
In hard disk drives, data are stored on surfaces of a plurality of rotatable disks mounted on a housing of the drive. Transducer heads that write data to and read data from the disk surfaces are supported by an actuator that positions the transducer heads in alignment with concentric data tracks defined on the disks. Each transducer head is attached to one end of a head suspension that is connected to an actuator arm that extends from the actuator body.
It has been common practice for hard disk drives to incorporate dual stage actuation swage mounts, for example, as shown in FIG. 1. FIG. 1 is a perspective illustration of a head suspension assembly 11 that may be connected to an actuator arm (not shown). The head suspension assembly may be swaged onto the actuator arm by inserting and swaging the hub 16 of a swage mount 15 into a hole in the actuator arm positioned above the disk. The head suspension assembly 11 may include a swage mount 12 having a flange portion 13 and a hub 16 surrounding an aperture of the flange portion 13 and extruding out of plane.
Primary actuation may be performed, for example, using a voice coil motor. In addition, at least one of a secondary actuation near the swage mount 15 or a direct movement of the head near the flexure 25 may be performed.
Piezoelectric transducers (PZTs) 17 may be provided as secondary actuators that mechanically position the head in a planar direction in response to applied electrical charge. The PZTs 17 actuate the head to move or vibrate in the x-z plane (see for example, the x, y and z axes shown in FIG. 3). The PZTs 17 may have conductive contacts 19. A hinge 21 may connect the swage mount 15 to a load beam 23 that acts as a spring that forces the head against the disk surface. A flexure 25 may be provided to locate the head, which is bonded underneath the flexure 25. The flexure 25 locates the head rigidly in the x-z plane while allowing the head to rotate about the x and z axes. In one embodiment, the head flies very close to the disk surface without contacting it in order to read and/or write very small magnetic bits. Rotation of the head maintains proper fly height and attitude.
In another embodiment, the swage mount 12 of FIG. 1 may extend into a tip (for example, with a ‘T’ shape) such that a stiffener 14 of the head suspension assembly 11 is eliminated, and the hinge 21 and the load beam 23 are welded to the tip as shown, for example in FIG. 2.
FIG. 2 is a top view illustration of a head suspension assembly 30 having a swage mount 31. The swage mount 31 has a flange portion 37 with a flange body 32 and a tip 33. A hub 35 extrudes out of plane from the flange body 32. The contacts 19 may connect the PZT 17 to a ground path. The contacts 19 may be epoxies for providing a conductive link between the swage mount 31 (for example, the ‘T’ shaped tip 33) and the PZTs 17.
FIG. 3 shows the swage mount 31 in isolation. The swage mount 31 includes a flange portion 37 having a flange body 32 and a tip 33. The tip 33 may be shaped, for example, similar to the letter ‘T.’ PZTs (similar to PZTs 17 discussed above with respect to FIG. 2) may be incorporated to bias the ‘T’ shaped tip 33 to deform substantially in-plane (in the x-z plane). As a result, positive or negative charges may be applied to the PZTs resulting in their expansion and/or contraction which then moves the head to align with the proper track for a read/write process on the underlying disk.
The swage mount 31 has a uniform thickness along the surface that extends from the flange portion 37 to the ‘T’ shaped tip 33. As the flange portion 37 and the tip 33 become thinner for providing additional clearance between the swage mount 31 and the disk underneath, the tip 33 becomes more susceptible to bending and/or twisting. The thin tip 33 lacks sufficient robustness for withstanding out-of-plane loads during shipping, handling, or assembly. Manufacturers in the art have sought to employ greater care in shipping, handling, or assembly methods, but such methods are costly and often ineffective in avoiding out-of-plane loads that cause permanent deformation of the swage mount and result in costly yield loss. Because the swage mounts known in the art have inadequate out-of-plane robustness, some manufacturers provide the swage mounts on a fret (a flat sheet for delivery of swage mounts) to help protect them, as shown in FIG. 4.
FIGS. 4-6 show swage mounts 31 with uniform thicknesses manufactured on a fret 39. A drawback of utilizing frets 39 is that the manufacturing process adds to processing and shipping costs. Manufacturing using frets 39 can also create cutting burrs and particles when the swage mount is removed from the strip along the trim line 34 before or after assembly. The burrs and particles have an adverse impact on drive reliability.
Beyond concerns involving shipping, handling, or assembly, the swage mounts known in the art suffer from poor drive performance. More particularly, the thin ‘T’ shaped tip 33 often has out-of-plane mechanical resonance modes that are too low in frequency and/or too high in amplitude, and has high displacements due to mechanical shock on the drive, resulting in poor drive performance.
There is a need in the art for a swage mount with higher manufacturing throughput and lower cost handling, shipping, and assembly in order to decrease the likelihood of permanent deformation of the swage mount or the tip. There is a need in the art for a swage mount that on the one hand, has a relatively thin flange body for providing sufficient clearance for the disk, and on the other hand, has a thicker tip with high out-of-plane yield robustness. Beyond shipping, handling, or assembly, it is critical for the tip to have favorable compliance in an in-plane direction (for example, along the x-z plane as shown in FIG. 3), yet robustness and high stiffness in an out-of-plane direction (for example, along the y axis as shown in FIG. 3) for high out-of-plane resonant frequencies, low out-of-plane resonant mode amplitudes, and small shock induced deformations, to achieve improved drive performance.